在原文书中看到这段落，但不清楚为什么要用as having had the flu
如果是因为要用had表达过去式，那为什么不直接写成 Or you "could" be misdiagnosed a
s having the flu.
At this point you might be saying, “Wait a minute! I’m sure that 95 percent of
the people I know have not had mono.” However, you can be exposed to Epstein–
Barr, develop mononucleosis, and simply never show any symptoms. Or you can be m
isdiagnosed as “having had” the flu. But 95 percent of the U.S. population doe
s have the antibodies for Epstein–Barr, which means they were once somehow infe
cted with it. And once you’ve caught the virus, it remains within your body for
the rest of your life, whether you feel sick or not.